Update purgecss suggested regex extractor.

[jsnanigans]

This fixes some issues people have been having. The regex A-z matches some symbols that might be unexpected, I found these but there could be more: `[]-_^
thats why we have changed it to A-Za-z_

[somebody32]

just tried that and on node 8, I'm getting SyntaxError: Invalid regular expression: /[A-Za-z0-9_-:\/]+/: Range out of order in character class. Were you thinking to escape - and not create a range ie /[A-Za-z0-9_\-:\/]+/g, because I'm not sure that _-: is a valid range

[jsnanigans]

@somebody32 could you please try this: /[A-Za-z0-9-_:\/]+/ apparently the order of _ and - matters

[adamwathan]

Hey thanks for the PR! Can you explain the issues you were seeing in more detail? I don't really see an issue with matching those other characters, in fact if anything I would probably want to make the regex even less strict because it's impossible to know what characters someone might be using in the keys in their config file.

[somebody32]

@adamwathan here is an example why using the previous one was problematic FullHuman/purgecss#75, maybe @jsnanigans has even more of them

[jsnanigans]

Hey @adamwathan, the main issue is that A-z gives unexpected results and cause quite a few problems to people.

Brought to out attention in this issue the expression A-z includes a lot of characters that are most likely not part of a selector.

A lot of people had problems with string literals - for example in this issue

A lot of the github issues for purgecss have something to do with A-z and by now almost all of those issues stem from the tailwind docs since we updated the default regex extractor some time ago.

Here are a few other issues related to this apart from the one @somebody32 mentioned:
FullHuman/purgecss#56
FullHuman/purgecss#83
FullHuman/purgecss#86

I guess I should have defined the issue better in the PR description :)

[adamwathan]

Got it, thank you for the history on the issue!